A bending-resistant multilayer ceramic substrate and preparation method thereof

Abstract

The present invention relates to the field of ceramic substrate technology and proposes a flex-resistant multilayer ceramic substrate and its preparation method. The flex-resistant multilayer ceramic substrate comprises the following raw materials by weight: 100 parts alumina, 2-4 parts sintering aid, 1-2 parts plasticizer, 1-2 parts reinforcing agent, 1-3 parts dispersant, 8-12 parts binder, and 85-90 parts water; the reinforcing agents include tungsten trioxide and cobalt trioxide. This technical solution solves the problem of low flexural strength in related multilayer ceramic substrates.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic substrates, and in particular to a bending-resistant multilayer ceramic substrate and a preparation method thereof. Background Art

[0002] Currently, in the preparation process of alumina multilayer ceramic substrates, 95wt% pure alumina is mostly used as raw material for cost and performance considerations. However, 95wt% pure alumina inevitably contains impurities such as SiO2 and Fe2O3, which will react to form a glass phase during the sintering process. The presence of the glass phase not only leads to a decrease in the bending strength of the alumina multilayer ceramic substrate, but also increases the dielectric loss.

[0003] To improve the flexural strength of alumina multilayer ceramic substrates, sintering aids are often added to increase the density and grain size of the substrates, thereby improving the flexural strength. However, this approach does not eliminate the problem of reduced flexural strength caused by the glass phase. Furthermore, excessive addition of sintering aids may also lead to a decrease in the flexural strength of the substrate, resulting in a flexural strength that cannot meet the requirements of use.

[0004] Therefore, it is necessary to provide a bending-resistant multilayer ceramic substrate to better meet the requirements of use and expand the scope of use of the alumina multilayer ceramic substrate. Summary of the Invention

[0005] The present invention provides a bending-resistant multilayer ceramic substrate and a preparation method thereof, which solves the problem of low bending strength of the multilayer ceramic substrate in the related art.

[0006] The technical solutions of the present invention are as follows:

[0007] The present invention provides a bending-resistant multilayer ceramic substrate, comprising the following raw materials in parts by weight: 100 parts of aluminum oxide, 2 to 4 parts of a sintering aid, 1 to 2 parts of a plasticizer, 1 to 2 parts of a reinforcing agent, 1 to 3 parts of a dispersant, 8 to 12 parts of a binder, and 85 to 90 parts of water; the reinforcing agent comprises tungsten trioxide and cobalt trioxide.

[0008] In the multilayer ceramic substrate of the present invention, the addition of a dispersant can improve the dispersibility of the powder in the raw material, reduce the agglomeration of the powder, and improve the uniformity of the slurry during the preparation process of the multilayer ceramic substrate. In addition, the uniformly dispersed powder can be more fully contacted during sintering, which can reduce the porosity and increase the density. This can not only improve the processing performance of the multilayer ceramic substrate during the preparation process, but also improve the bending strength of the multilayer ceramic substrate.

[0009] In the multilayer ceramic substrate of the present invention, the addition of a plasticizer can improve the rheological properties of the ceramic powder slurry, enhance the formability and processability of the green body, reduce the friction between the powders during the preparation of the multilayer ceramic substrate, increase the flexibility of the green body, make the green body easier to deform without breaking during molding, and reduce the risk of cracks in the multilayer ceramic substrate.

[0010] As a further technical solution, the purity of the aluminum oxide is 95%, and it is prepared using brown corundum as raw material.

[0011] As a further technical solution, the reinforcing agent further includes zirconium oxide.

[0012] In the multilayer ceramic substrate of the present invention, the reinforcing agent further comprises zirconium oxide. The addition of zirconium oxide can further improve the flexural strength of the multilayer ceramic substrate on the basis of tungsten trioxide and cobalt trioxide. Zirconium oxide can promote the transformation of the glass phase to the crystalline phase by providing crystal nucleation sites, thereby further improving the flexural strength of the multilayer ceramic substrate.

[0013] As a further technical solution, when the reinforcing agent is composed of tungsten trioxide, cobalt trioxide and zirconium oxide, the mass ratio of tungsten trioxide, cobalt trioxide and zirconium oxide is 5:1:1~2, for example, it can be 5:1:1, 5:1:2, 5:1:1.5, 5:1:1.8, 5:1:2, and preferably 5:1:1.5.

[0014] In the multilayer ceramic substrate of the present invention, the proportions of the various components in the reinforcing agent composed of tungsten trioxide, cobalt trioxide, and zirconium oxide are limited. By limiting the ratio of the three, the role of zirconium oxide in providing crystal nucleation sites can be better utilized, promoting the transformation of tungsten trioxide and cobalt trioxide from the glass phase to the crystalline phase, reducing the content of the glass phase, and further improving the bending strength of the multilayer ceramic substrate.

[0015] As a further technical solution, the dispersant includes polyacrylic acid.

[0016] As a further technical solution, the sintering aid includes one or more of yttrium oxide, calcium oxide, and lanthanum oxide.

[0017] In the multilayer ceramic substrate of the present invention, the addition of a sintering aid can multi-dimensionally control the density of the multilayer ceramic substrate, refine the grains, reduce the glass phase, inhibit the abnormal growth of the grains, and improve the bending strength of the multilayer ceramic substrate.

[0018] As a further technical solution, the plasticizer includes one or both of polyethylene glycol and polypropylene alcohol.

[0019] As a further technical solution, the binder includes one or both of polyvinyl alcohol and hydroxypropyl methylcellulose.

[0020] The present invention also provides a method for preparing a bending-resistant multilayer ceramic substrate, which comprises the following steps:

[0021] S1. Mixing alumina, a plasticizer, a sintering aid, a reinforcing agent, a dispersant, and water to obtain a mixture;

[0022] S2, adding a binder to the mixture to obtain a slurry, and forming the slurry by tape casting and drying to obtain a green porcelain sheet;

[0023] S3, punching the green ceramic sheet, performing surface printing, laminating, upper and lower conductive bonding, cutting, sintering, and cooling to obtain a bending-resistant multilayer ceramic substrate.

[0024] As a further technical solution, during the sintering, the temperature is 1450° C. and the time is 3 hours.

[0025] As a further technical solution, in step S3, the cooling is to sinter at 1450°C for 3 hours, first cool to 900°C at a rate of 10°C / min, then cool to 700°C at a rate of 2~8°C / min, and finally cool to room temperature at a rate of 15°C / min.

[0026] As a further technical solution, in step S3, the cooling is to sinter at 1450°C for 3 hours, first cool to 900°C at a rate of 10°C / min, then cool to 700°C at a rate of 5°C / min, and finally cool to room temperature at a rate of 15°C / min.

[0027] The present invention limits the cooling rate during the preparation of multilayer ceramic substrates, which can improve the fracture toughness of multilayer ceramic substrates. The cooling rate affects the crystallization nucleation and growth rate of the glass phase. Too fast a cooling rate makes it difficult for the glass phase to crystallize, while too slow a cooling rate results in the formation of coarse crystals. The present invention limits the cooling process to three stages during the preparation of multilayer ceramic substrates, which can promote the transformation of the glass phase into the crystalline phase. The volume expansion generated during this transformation can inhibit crack propagation, thereby improving the fracture toughness of the multilayer ceramic substrate.

[0028] The working principle and beneficial effects of the present invention are:

[0029] In the present invention, a reinforcing agent composed of tungsten trioxide and cobalt tetroxide and a sintering aid are added to the multilayer ceramic substrate, which significantly improves the flexural strength of the multilayer ceramic substrate. In the prior art, in order to improve the flexural strength of the multilayer ceramic substrate, sintering aids are often added for the purpose of increasing density and refining grains, but the improvement in the flexural strength of the multilayer ceramic substrate is limited. The present invention also focuses on the effect of the phase transition of the glass phase formed by aluminum oxide impurities on the flexural strength of the multilayer ceramic substrate. By adding reinforcing agents including tungsten trioxide and cobalt tetroxide, the stability of the glass phase can be reduced, the melting temperature and high-temperature viscosity of the glass phase can be reduced, the diffusion rate of ions in the liquid phase can be accelerated, crystals can be more easily formed, and the transformation of the glass phase to the crystalline phase can be promoted. Experiments have shown that the joint addition of the two can significantly improve the flexural strength of the multilayer ceramic substrate and expand the scope of use of the multilayer ceramic substrate. DETAILED DESCRIPTION

[0030] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0031] In the following examples and comparative examples:

[0032] Alumina has a purity of 95wt% and an average particle size of 25μm, and is produced by high-temperature smelting using brown corundum as the raw material. Tungsten trioxide has an average particle size of 20nm; cobalt trioxide has an average particle size of 100nm; and yttrium oxide has an average particle size of 50nm. The viscosity of hydroxypropyl methylcellulose is 100,000 mPa·s. The model of polyethylene glycol is PEG-1000. The weight-average molecular weight of polyacrylic acid is 1800.

[0033] Example 1

[0034] A method for preparing a bending-resistant multilayer ceramic substrate comprises the following steps:

[0035] S1. Mixing 100 parts of aluminum oxide, 1 part of polyethylene glycol, 2 parts of yttrium oxide, 1 part of a reinforcing agent, 1 part of polyacrylic acid, and 85 parts of water to obtain a mixture;

[0036] S2, adding 8 parts of hydroxypropyl methylcellulose to the mixture to obtain a slurry, and the slurry is tape-casted and dried to obtain a green porcelain sheet;

[0037] S3, after punching the green ceramic sheet, surface printing, lamination, upper and lower conductive, cutting, sintering at 1450 ° C for 3 hours, first cooling at a rate of 10 ° C / min to 900 ° C, then cooling at a rate of 2 ° C / min to 700 ° C, and finally cooling at a rate of 15 ° C / min to room temperature, to obtain a bending-resistant multilayer ceramic substrate;

[0038] The enhancer is composed of tungsten trioxide and cobalt tetroxide in a mass ratio of 5:1.

[0039] Example 2

[0040] A method for preparing a bending-resistant multilayer ceramic substrate comprises the following steps:

[0041] S1. Mixing 100 parts of aluminum oxide, 2 parts of polyethylene glycol, 4 parts of yttrium oxide, 2 parts of a reinforcing agent, 3 parts of polyacrylic acid, and 90 parts of water to obtain a mixture;

[0042] S2, adding 12 parts of hydroxypropyl methylcellulose to the mixture to obtain a slurry, and the slurry is tape-casted and dried to obtain a green porcelain sheet;

[0043] S3, after punching the green ceramic sheet, surface printing, lamination, upper and lower conductive, cutting, sintering at 1450 ° C for 3 hours, first cooling at a rate of 10 ° C / min to 900 ° C, then cooling at a rate of 2 ° C / min to 700 ° C, and finally cooling at a rate of 15 ° C / min to room temperature, to obtain a bending-resistant multilayer ceramic substrate;

[0044] The enhancer is composed of tungsten trioxide and cobalt tetroxide in a mass ratio of 5:1.

[0045] Example 3

[0046] Compared with Example 1, the only difference of this embodiment is that the reinforcing agent is composed of tungsten trioxide, cobalt trioxide and zirconium oxide in a mass ratio of 5:1:1.

[0047] Example 4

[0048] Compared with Example 1, the only difference of this embodiment is that the reinforcing agent is composed of tungsten trioxide, cobalt trioxide and zirconium oxide in a mass ratio of 5:1:1.5.

[0049] Example 5

[0050] Compared with Example 1, the only difference of this embodiment is that the reinforcing agent is composed of tungsten trioxide, cobalt trioxide and zirconium oxide in a mass ratio of 5:1:2.

[0051] Example 6

[0052] Compared with Example 4, the only difference of this embodiment is that the reinforcing agent is composed of tungsten trioxide, cobalt trioxide and zirconium oxide in a mass ratio of 1.5:1:5.

[0053] Example 7

[0054] Compared with Example 4, the only difference of this embodiment is that the cooling in step S3 is first cooling to 900°C at a rate of 10°C / min, then cooling to 700°C at a rate of 5°C / min, and finally cooling to room temperature at a rate of 15°C / min.

[0055] Example 8

[0056] Compared with Example 4, the only difference of this embodiment is that the cooling in step S3 is first cooling to 900°C at a rate of 10°C / min, then cooling to 700°C at a rate of 8°C / min, and finally cooling to room temperature at a rate of 15°C / min.

[0057] Comparative Example 1

[0058] Compared with Example 1, the only difference of this comparative example is that the reinforcing agent is only tungsten trioxide.

[0059] Comparative Example 2

[0060] Compared with Example 1, the only difference of this comparative example is that the reinforcing agent is only cobalt trioxide.

[0061] Comparative Example 3

[0062] Compared with Example 1, the only difference of this comparative example is that no reinforcing agent is added.

[0063] Comparative Example 4

[0064] Compared with Example 1, the only difference of this comparative example is that the reinforcing agent is replaced by an equal amount of yttrium oxide.

[0065] Experimental example

[0066] The performance of the multilayer ceramic substrates in Examples 1 to 8 and Comparative Examples 1 to 4 was measured using the following method:

[0067] (1) Fracture toughness: The fracture toughness was determined according to the method in GB / T 23806-2009 “Fine Ceramics Fracture Toughness Test Method Single Edge Precracked Beam (SEPB) Method”;

[0068] (2) Flexural strength: Test the flexural strength of the specimen according to the test method (three-point bending method) specified in GB / T 6569-2006 “Test method for flexural strength of fine ceramics”;

[0069] (3) Dielectric constant: The dielectric constant at 10 GHz was measured according to the method in GB / T 12636-1990 "Stripline test method for complex dielectric constant of microwave dielectric substrates";

[0070] The measurement results are shown in Tables 1 to 3.

[0071] Table 1 Bending strength test results of multilayer ceramic substrates in Examples 1 to 6 and Comparative Examples 1 to 4

[0072]

[0073] As shown in Table 1, the bending strengths of Examples 1 to 6 of the present invention are all higher than those of Comparative Examples 1 to 4, indicating that the addition of a reinforcing agent to the multilayer ceramic substrate of the present invention can improve the bending strength of the multilayer ceramic substrate.

[0074] Table 2 Fracture toughness test results of multilayer ceramic substrates in Examples 4, 7, and 8

[0075]

[0076] As can be seen from Table 2, the fracture toughness of the multilayer ceramic substrate can be improved by limiting the cooling rate during the preparation process of the multilayer ceramic substrate in the present invention.

[0077] Table 3 Dielectric constant measurement results of multilayer ceramic substrates in Example 1, Example 4, and Comparative Example 3

[0078]

[0079] As shown in Table 3, in the present invention, by adding the additives consisting of tungsten trioxide, cobalt trioxide and zirconium oxide into the multilayer ceramic substrate, the multilayer ceramic substrate can have a lower dielectric constant.

[0080] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A bending-resistant multilayer ceramic substrate, characterized in that: The raw materials include the following components in parts by weight: 100 parts of aluminum oxide, 2-4 parts of sintering aid, 1-2 parts of plasticizer, 1-2 parts of reinforcing agent, 1-3 parts of dispersant, 8-12 parts of binder, and 85-90 parts of water; the reinforcing agent includes tungsten trioxide and cobalt trioxide.

2. The bending-resistant multilayer ceramic substrate according to claim 1, characterized in that: The reinforcing agent also includes zirconium oxide.

3. The bending-resistant multilayer ceramic substrate according to claim 2, characterized in that: When the reinforcing agent consists of tungsten trioxide, cobalt trioxide and zirconium oxide, the mass ratio of the tungsten trioxide, cobalt trioxide and zirconium oxide is 5:1:1-2.

4. The bending-resistant multilayer ceramic substrate according to claim 1, characterized in that: The dispersant includes polyacrylic acid.

5. The bending-resistant multilayer ceramic substrate according to claim 1, characterized in that: The sintering aid includes one or more of yttrium oxide, calcium oxide, and lanthanum oxide.

6. The bending-resistant multilayer ceramic substrate according to claim 1, characterized in that: The plasticizer includes one or both of polyethylene glycol and polypropylene alcohol.

7. The bending-resistant multilayer ceramic substrate according to claim 1, characterized in that: The binder includes one or both of polyvinyl alcohol and hydroxypropyl methylcellulose.

8. A method for preparing a bending-resistant multilayer ceramic substrate, for preparing the bending-resistant multilayer ceramic substrate according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Mixing alumina, a plasticizer, a sintering aid, a reinforcing agent, a dispersant, and water to obtain a mixture; S2, adding a binder to the mixture to obtain a slurry, and forming the slurry by tape casting and drying to obtain a green porcelain sheet; S3, punching the green ceramic sheet, performing surface printing, laminating, upper and lower conductive bonding, cutting, sintering, and cooling to obtain a bending-resistant multilayer ceramic substrate.

9. The method for preparing a bending-resistant multilayer ceramic substrate according to claim 8, wherein: In step S3, the cooling is as follows: after sintering at 1450°C for 3 hours, the temperature is first lowered to 900°C at a rate of 10°C / min, then lowered to 700°C at a rate of 2-8°C / min, and finally lowered to room temperature at a rate of 15°C / min.

10. The method for preparing a bending-resistant multilayer ceramic substrate according to claim 9, characterized in that: In step S3, the cooling is as follows: after sintering at 1450°C for 3 hours, first cooling to 900°C at a rate of 10°C / min, then cooling to 700°C at a rate of 5°C / min, and finally cooling to room temperature at a rate of 15°C / min.

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